Gas Generator For Splitting And Destructing Materials, Ignition Unit And Composition For Use In Gas Generators

ABSTRACT

A gas generator device ( 3 ) is used for breaking or splitting natural and artificial objects when inserted in a drilled hole and ignited to start a burning reaction in a deflagration or non-detonation mode. The gas generator comprises a first part ( 11 ) having a first main cavity ( 12 ) and a second part ( 13 ) having a second main cavity ( 14 ). An oxidant and a combustible compound are contained in the first part. A liquid such as water is contained in the second main cavity for distributing the pressure obtained from gases generated in the burning reaction. The first and second main cavities are separated from each other by a bottom plate ( 21 ) of the first part that e.g. can be set at a level to adapt the volume of the first space and the amount of oxidant contained therein. The gas generator device is particularly well suited for use in horizontal drilled holes. The first part can comprise a composition using as part of the combustible compound a holding structure of polymer material and added thereto, aluminium or a similar material which reduces the burning time and increases the energy content of the composition. A special ignition unit ( 27 ) can be used.

RELATED APPLICATIONS

This application claims priority and benefit from Swedish patentapplications Nos. 0801781-6, filed Aug. 11, 2008, 090002-5, filedJanuary, 2009, and 0900044-9, filed January, 2009, the entire teachingsof which are incorporated herein by reference.

TECHNICAL FIELD

The present invention is related to a gas generator for use in drilledholes for generally splitting rocks or stone blocks and particularly fordestruction of objects in a gentle mode, e.g. for use in the field oftunnel construction and also in the mining and quarrying industry. Theinvention is also related to an ignition unit for igniting charges ofslowly burning compositions. Furthermore, the invention is related to acomposition based on chlorates and perchlorates of alkaline metals andorganic compounds for use in gas generators of the above kind.

BACKGROUND

For breaking or splitting stiff objects such as stone blocks or blocksof rock in gentle, avoiding disadvantages that can be associated withthe use of ordinary explosives, a deflagration reaction, i.e. a rapidburning of a specially selected fuel, can be used. The burning velocityin a deflagration reaction is smaller than that of an explosive, anexplosive defined to have a detonation reaction with a burning velocitygreater than the velocity of sound. A way of using deflagration forbreaking an object comprises drilling shafts along the line of a plannedrupture, inserting into the drilled shafts charges of liquid and solidreagents selected to have the intended non-detonation reaction ofburning, then sealing the shafts and finally igniting the charges tostart the non-detonation reaction. The charges can comprise a solid fueldesigned as tubes or diaphragms having longitudinal directions parallelto the direction of fire progress and to the shafts. Inside and betweenthe tubes or between the diaphragms a fine powder or generally agranular mixture of an oxidant such as NaClO₃ and other fuels such as aliquid fuel and possibly some suitable metal is placed.

Thus, in the Russian patent No. 2211923 a gas generator (GG) isdisclosed that has a body made from a combustible agent and has channelsin which an oxidizer is contained. The channels can be formed asparallel channels e.g. in the inner spaces of a plurality of paralleltubes. The gas generator is suited for reacting in a gentle,non-detonation mode and producing a sufficient amount of gases forbreaking stone and similar materials.

A similar gas generator is disclosed in Swedish patent 0201972-7 havingpublication No. 523 163 and it additionally contains an amount of aliquid combustible agent, such as a hydrocarbon, which is filled intothe inner spaces of the tubes or body structure, after having filledthem with the oxidizer, the body structure made from solid hydrocarbonpolymer material.

These prior gas generators can have the following advantages:

1. Stability and homogeneity of the oxidizer compound across and alongeach channel in the gas generator.2. There is a minimum variation of the composition between different gasgenerators and between different element tubes.3. The cross-section of an element tube of a gas generator can have theshape of a circular ring, a hexagon ring, a square ring and any othershape which ensures the most dense packing of the channels that areoriented along the axis of the gas generator.

However, these prior art gas generators can have several disadvantages,especially when working with horizontal holes. When using such a gasgenerator for long drilled holes a pressure distributing medium such assand can be used. The sand is loaded at the bottom of the holes whichcan be carried out using paper tubes filled with sand and e.g. having alength of about 0.25 m. The number of paper tubes required is determinedby the length of the hole. For a length of 1.5 m about eight such tubesare required. It can be difficult to automatize such a process offilling in particular long horizontal holes since a multitude of sandtubes are required.

In the gas generators an ignition unit must be used for igniting therespective charge. Such ignition units for igniting charges of slowlyburning compositions should be mechanically stable so that there is norisk of damaging the ignition compound contained therein. Also, theignition fuses and in particular the ignition compounds should be easilyand safely loaded in the ignition units.

In gas generators of the kind described above and similar ones acomposition is used which when ignited burns in a more or less rapid wayproducing gases of a high volume. Such compositions are generally usedin the field breaking or destructing materials.

Thus, e.g. explosives based on ammonium nitrates are widely used, seeDubnov, L. V., Baharevich, H. S., Romanov, A. I., “Industrialexplosives”, Nedra, 1973. p. 320. Most of them have favourableproperties. Explosives based on potassium chlorate and/or potassiumperchlorate together with explosives based on ammonium perchlorate wereused during the First World War in France, the United Kingdom andGermany for charges in shells and bombs, see Ligotskij, D. N., “Granitelosses at delivering and elaboration: Problems of theory of planningmines”, Inter University Proceedings. St-Pb, 1955. pp. 76-77, and Kotov,L. R., Kytsenko, Y. C., Kylakevich, Y. S., “Hose charges for chippinggranite blocks/Physical problems of destroying massive rocks”,Proceedings of the International Scientific Conference, Moscow, Sep.7-11, 1999, pp. 217-218. However, when using the above mentionedcompositions for splitting stone blocks into smaller parts which areintended for use in the quarrying industry for producing e.g. buildingstones, the output may not be more than 20%, see the cited article byLigotskij, because of the high forces produced during the explosionprocess. In order to reduce the risks associated with explosionsproduced by common explosives a more gentle mode of the explosiveprocess can be used. Various methods and means for achieving gentleexplosions have been invented, for instance using charges having areduced share of the explosive substance or using soft charges having,in addition to the explosive substance, inert filling materials such aswater or air, encapsulated in some suitable way, as is disclosed in thecited article by Kotov et al. In the recent years when mining blockstone one has tried to use materials which produce the pressure in theblast holes in a deflagration mode, instead of the commonly useddetonation mode for ordinary explosives, or in a low-speed detonationmode. However, the use of explosive compositions having a reduceddetonation speed, e.g. Granilene-1,2,3, Forcite, Gourite, only partlysolves this problem since the costs of these compositions are higher,there may be resulting environment problems, etc.

In some mines black blasting powder is still used but the dangerousnessthereof is well known. However, the use of black blasting powder as wellthe above mentioned compositions in obtaining stone blocks from largerrocks can to some extent be understood due to their dynamicalparameters, in particular the short reaction time that may range from afew microseconds to several milliseconds.

Currently, compositions based on sodium chlorate (NaClO₃) andhydrocarbons (C_(x)H_(y)), that can be in a solid or liquid form, e.g.polymers such as polyethylene, polypropylene, mineral oils such asDiesel fuel, are of a special interest due their low cost and thepossibility of automatizing both the transport thereof and the chargingoperations. Also, such compositions can be finally prepared directly inthe field, on the place where they are to be used, which increases worksafety. According to provisional thermodynamic calculations the workingcapacity (RT) of the products of the explosion for the main component ina composition based on a stoichiometric mixture of NaClO₃ and C_(x)H_(y)(in such a mixture the number of oxygen atoms exactly matches the numberof carbon and hydrogen atoms for the reactions 2 O+C→CO₂ and O+2 H→H₂O)is about 720 kJ/kg. Even larger RTs can be obtained when usingcompositions also including aluminium and based on perchlorates insteadof chlorates, preferably ammonium perchlorate. However, an extendedfurther use of such composition has been restricted, basically due thehigh cost, especially of the ammonium-based ones, see the cited book byDubnov et al. Nowadays they have some use only in Japan (carlites) andpartly in France (sevronites). Chlorate-based compositions have a lowercost and are more safe in use.

Another advantage of compositions based on perchlorates and chlorates istheir higher original density when compared to compositions based onammonium nitrate. Thus, the density of ammonium nitrate is 1730 kg/m³whereas the density of sodium chlorate is 2490 kg/m³, see Shraiber, S.S., “Producing Berthollet's salt and other chlorates”, GONTI NKTP, 1938,p. 367.

The explosive composition for use in blast holes disclosed in RussianFederation patent No. 2152376 and in the above cited Swedish patent0201972-7 contains 7-11% liquid hydrocarbons and 17.3-20.9% solidhydrocarbon polymer material where the rest is sodium chlorate. Thiscomposition allows that explosives having a detonation mode as well as adeflagration, non-detonation mode of burning are obtained. Adeflagration mode of the burning of the composition can be obtained byproviding the solid material, i.e. the solid hydrocarbon polymermaterial, in a suitable shape enclosing or holding the other componentsof the composition, such a shape e.g. including a plurality of tubes, a“honeycomb” structure, corrugated strips or sheets. A disadvantage ofthe composition disclosed in the Russian Federation patent No. 2152376and the cited Swedish patent when using it in a gentle destruction mode,such as in a deflagration mode of burning, and especially when it isused without the liquid component, in blast holes in materials of highstrength as well as in fissured rock is that it may have a low burningvelocity, due to a too small energy content of the composition, givingin an insufficient velocity of the pressure build-up in the blast holesproduced by the evolved gases. This can in some cases be compensated forusing a larger mass of the composition, this however increasing the costof the explosive composition per blast hole. Also, the pressure build-upcan be so slow that it will not split the rock where the blast hole ismade.

SUMMARY

It is an object of the invention to provide a gas generator forsplitting or destructing materials, in which the above mentioneddisadvantages of prior gas generators are reduced and the advantages arepreserved.

It is an object of the invention to provide an ignition unit forigniting slowly burning materials which allows a high degree of safetyin the handling thereof.

It is an object of the invention to provide a composition that has asufficient speed of burning as well as a sufficient energy content andthat can be directly used, without mixing any components, in the fieldfor splitting or destructing materials, while preserving the basicadvantages of the composition disclosed in the cited Swedish patent0201972-7.

Thus generally, a gas generator is provided for splitting, in a gentlemode, rock, block stones and similar objects, thus generally fordestructing natural and artificial objects.

Generally, a gas generator is designed to have two main, separatecavities or spaces or generally two parts. In the first part or firstmain space material for burning in a gentle mode are provided. The firstpart can e.g. be configured according to the cited Russian patent2211923 and/or the first cavity can be filled with material as disclosedin the Russian patent 2153069 or in the Russian patent 2152376 or aswill be described hereinafter. The first part can also be designedsubstantially as disclosed in the cited Swedish patent 0201972-7. Thesecond cavity which is located in the second part is filled with aliquid such as a substantially incompressible liquid, e.g. water. Theliquid is closed from the first cavity body at least by the bottom plateof the first part and of the first cavity.

The gas generator can have advantages such as reducing the amount oftime used for loading a horizontal hole since the main part of the holeis occupied by the part of the gas generator that is filled with aliquid. Also, due the pressure distributing effect of the part filledwith a liquid a smaller amount of explosive or burning material may beused. For example, for drilled holes longer than 2.5 m it has previouslybeen proposed that two gas generators having weights of 120 and 90 gramsshould be used whereas with the gas generator described herein acomposition having the weight of 150 g placed in the fuel area of thegas generator is enough. Obviously, also the use of a slower burningprocess compared to conventional explosives may have advantages such asa generally “softer” operation, i.e. a smaller noise level, a smallerdeviation of the crack actually produced from the intended crackingline, etc.

In a different aspect, an ignition unit is provided which is generallyadapted or suited for igniting charges of slowly burning substances, inparticular for igniting a charge such as in a gas generator adapted tosplit, in a gentle mode, rock, block stones and similar objects, thusgenerally to destruct natural and artificial objects. The ignition unitcomprises an ignition fuse that includes a cavity containing an ignitioncompound. The ignition fuse is at its sides surrounded by a free bufferspace located inside an outer protective shell. The buffer spaceprotects the ignition fuse and the ignition compound contained thereinwhen the ignition unit is stored and handled, such as when it is beingmounted it to a charge or a gas generator.

The ignition unit can include a body having substantially a cup shape orbowl shape, the body then including a lid from which the outerprotective shell projects. The body can further include a holdingstructure inside the outer shell such as an inner shell for holding theignition fuse. Then the free buffer space is formed between the outershell and the holding structure such as the inner shell. The inner shellcan then have an inner space receiving the ignition fuse. The shapes ofthe inner space and the ignition fuse may be adapted so that theignition fuse is securely held in the inner space. Also, the shape ofthe inner space and the ignition fuse can be adapted so that theignition fuse can be easily introduced in the inner space. The ignitionfuse can thus be a unit separate from the body but connectable thereto.It may also be separated from the body for e.g. checking the ignitioncompound. This allows the ignition fuse to be stored separately andloaded in the ignition unit when it is to be used such as when a gasgenerator is to be mounted in a drilled hole, this providing an easy andsafe handling of the part containing the ignition compound.

Furthermore, the ignition fuse can have a bottom which delimits thecavity and which, when the ignition unit is adapted for igniting acharge, is directed to or facing a surface of the charge, and it hasalso sidewalls that delimit the cavity and are connected to the bottomand extend away from the surface of the charge. The sidewalls may have athickness that is considerably larger than the thickness of the bottom,so that when the ignition unit is activated and the ignition compound ismade to burn, a jet of hot material is produced and emitted from thecavity containing the ignition compound, breaking the bottom of thecavity and the jet being directed towards the surface of the charge. Thejet is thus formed in the free space at the inner end of the ignitionfuse and is relatively well localized and narrow. By this arrangement,the jet only hits a relatively small surface area of the charge to beignited. The heating power of the ignition compound is thus highlyconcentrated and has a high energy that may also ignite charges that arerelatively safe or “slow”, i.e. are not easily ignited.

Such a design of the ignition unit may give a high degree of safety whenhandling it. The ignition unit may also be very easily handled andloaded, not requiring e.g. any welding operation.

In another aspect, a composition is provided for use when splitting, ina gentle mode, rock, block stones and similar objects, thus generallyfor destructing natural and artificial objects, and it comprises a solidoxidant, e.g. based on chlorate or perchlorate, such as one or more ofthe compounds sodium chlorate, potassium chlorate, sodium perchlorateand potassium chlorate, and a solid wall material substantially of ahydrocarbon polymer material, the solid wall material provided in asuitable shape, in particular in the shape of tubes, a honeycombstructure, corrugated strips or sheets or a plurality of containersholding or enclosing other components of the composition. Thecomposition is suitably placed in or arranged as a gas generator.

The solid material comprises a burning velocity enhancing material, inparticular aluminium or a similar metal. The burning velocity enhancingmaterial can have a concentration of 1.0-15 wt % of the total mass ofthe composition, the concentration of the solid hydrocarbon materialtogether with the burning velocity enhancing material can be 5-21 wt %of the total mass of the composition, and the rest of the total mass ofthe composition can substantially be sodium chlorate.

The solid hydrocarbon polymer material may e.g. be one or more ofpolyethylene, polypropylene, polystyrene and similar polymers.

The composition can be used in the gas generator described above but theuse thereof is not limited thereto. The composition can be used whenevera fast or slow burning material is required such as for splitting ordestructing materials.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of non-limiting embodimentswith reference to the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of a gas generator device,

FIG. 2 is a view similar to FIG. 1 of an alternative embodiment of a gasgenerator device,

FIGS. 3 and 4 are similar to FIG. 1 but of gas generator devicescomposed of two detachable parts,

FIG. 5 is a schematic picture of a hole drilled in an object to besplit, the hole containing gas generator devices including two separateparts,

FIG. 6 is a schematic picture of an object to be split,

FIG. 7 is schematic, cross-sectional view of an ignition unit,

FIG. 8 is a similar to FIG. 7 of a slightly modified ignition unit, and

FIG. 9 is a cross-sectional view of a simple gas generator.

DETAILED DESCRIPTION

In splitting rocks, such as for constructing a tunnel, shafts or holes 1can be drilled as outlined in FIG. 6. In the holes a gas generator 3 isinserted to be located at some depth in the hole. The gas pressuregenerated when the gas generator is ignited to burn is distributed tothe walls of the drilled hole 1 by a fluid medium 5 placed in the holebetween the gas generator and the bottom of the hole, the opening of thehole being blocked by a plugging device 7. The fluid medium can be asubstantially incompressible liquid such as water. If the region of thehole left for the plugging device has a sufficient length, e.g. of about1.5 m for a hole diameter of 32 mm (1¼″), the plugging device can bemade from e.g. ordinary sand that can have particle diameters in therange of 0.5-2 mm and is densely packed into the opening region of thehole. If the length is not sufficient, a wooden plug, not shown, mayadditionally be used.

There may be a problem in applying the fluid medium 5 in the drilledholes 1, in particular when they are substantially horizontal or aredirected upwards, taken from their mouths or openings. Additionally, insome cases such substantially horizontal holes or holes directed upwardscan have a considerable length, e.g. of 3-5 m, this making theapplication of the fluid even more difficult.

One way of solving this problem is to incorporate the fluid medium 5 inthe gas generator 3. Thus, the gas generator is extended to include botha first part 11 containing a first main space or cavity 12 and a secondpart 13 containing a second main space or cavity 14, see FIGS. 1 and 2.

In the first part 11 or first main space 12 material is provided forburning, e.g. in a gentle mode. The first part can e.g. be configuredsubstantially as disclosed in the cited Russian patent 2211923 or thecited Swedish patent 0201972-7 and/or the first cavity can beconstructed and/or filled with material as disclosed in the Russianpatents 2153069 or 2152376 or it can built as will be described below.As seen in the figures, the first part can contain a plurality ofparallel channels 15 that together form the first cavity 12 and that arefilled with a suitable composition. The filling can e.g. include asuitable oxidizer such as one or more chlorates and/or perchlorates ofalkaline metals and/or earth metals, e.g. sodium chlorate NaClO₃, andsome combustible material such as a hydrocarbon compound and/or asuitable polymer, e.g. a hydrocarbon polymer such as polyethylene,polypropylene and/or polystyrene. Also the walls 17, 19 of the channels15 can if desired or suitable by made from a combustible material. Thechannels are at the bottom of the first main cavity 12 closed by abottom plate 21 and at the top of the first main cavity closed by a topplate 23. At the top plate, e.g. in a space 25 closed by a top plug 27,an igniter 29 can be arranged.

The channels 15 can be formed by a multitude of tubes placed at thesides of each other, e.g. tubes having a circular cross-section.Alternatively, the channels can have a polygon shape, such as a squareor generally rectangular cross-section formed by straight partitionwalls perpendicularly crossing each other or a honey-comb structure orbe formed by an accordion-like structure or corrugated foil arrangedinside the outer wall 17 as disclosed in the cited Swedish patent0201972-7.

The second cavity 14 in the second part 13 is filled with the fluidmedium 5, i.e. a liquid, that as above can be a substantiallyincompressible liquid e.g. water. The second part thus is substantiallya container for the fluid medium 5 and can be called a container partwhereas the first part 11 is the proper gas generator part. The walls 30of the second part can be made from any suitable material that isimpermeable to the liquid used and has sufficient mechanical strength toallow handling of the second part, in particular for introducing it intoa drilled hole. E.g. impregnated paper, a polymer material, such aspolyethylene or rubber, or a metal such as aluminium can be used, atleast partly in the second part. The second cavity is delimited from thefirst cavity 13 by the bottom plate 21 of the first cavity 12.

As shown in FIG. 1 the outer walls of the first and second cavities 12,14 can formed by an integral common tube 17 that thus can be made in onepiece and/or from only one material. The tube has a bottom 18 alsoforming the bottom or inner end of the second cavity. Alternatively, theouter walls can be formed by a tubular structure formed by a first tubepart 17′ extending over the first cavity 12 and a second tube part 17″being the substantial portion of the outer wall of the second cavity 14.The two tube parts can be made from different materials, for example sothat the second tube part has walls that are thinner than those of thefirst tube part. Hence, the second tube part 17″ can e.g. be collapsibleso that it can be stored, when it does not contain any liquid, in afolded-in or rolled-up state.

The sizes of the cavities 12, 14 are determined by the depth of the hole1 and the strength of the material to be destroyed. For example, thesize of the cavity 12 could for granite be set as to contain 90 g of thefuel for a length of 1.5 m of the hole 1 located inside the plug 7, thediameter of the hole being 32 mm.

The material of the bottom plate 21 should be chosen to allow a longcontact with the oxidant used, and e.g. polyethylene, polypropylene,polystyrene etc. may be used. Suitably, such polymers can be used intheir expanded or foamed states, such as foam polyethylene, foampolypropylene or foam polystyrene, in order to e.g. reduce the weight ofgas generator 3. The bottom plate must tightly seal the first and secondcavities from each other, in particular so that there is no risk ofhaving the liquid present in the second cavity 14 penetrating into thefirst cavity 12.

The first part 11 of the gas generator 3 can be loaded in the followingway:

1. Putting the bottom plate 21 at the height required by the amount ofcomposition to be filled into the first cavity 12.2. Loading tubes, a honeycomb structure or corrugated foil, the walls ofwhich are seen at 19, of a suitable length.3. Loading the required amount of oxidant according to calculations intothe channels 15 formed and if required also a combustible compound.4. Installing the top plate 23 over the tubes, honeycomb structure etc.5. Mounting a simple top plug 27.

When the gas generator 3 is to be used by an end user, he can dismountthe simple top plug 27 and instead install another top plug integratedwith an igniter 29 or possibly an igniter made as a separate unit andthen remount the simple top plug. The igniter is connected to electricalcables, not shown, for activation. Then, the complete assemblycomprising the two parts 11, 13, the cavity 14 of the second part filledwith the liquid, is inserted, using e.g. a wooden bar, not shown, into adrilled hole 1 until it is stopped by contact of the inner side orbottom of the second part with the bottom of the hole, the electricalcables to the igniter being held tensed during this operation. In thecase where a plugging device made from a filling with sand is to beused, the total length of the gas generator including the part filledwith liquid should be determined in such a way that there is at least alength of 1.5 m of free space from the top of the gas generator 3 to thesurface of the rock. Finally then, the sand for plugging the hole 1 isinserted in the free space at the opening of the hole according totested technology. For example, paper tubes, not shown, filled with sandand having lengths of 0.25 m can be used. The first paper tube isinserted to come in contact with the already introduced gas generator 3,but without using a strong pressing force. The following paper tubes areinserted with stronger pressing forces, using e.g. the wooden bar,compressing the sand firmly to break the paper envelopes and to get afirm grip to the walls of the drilled hole 1. If there is a shorter freespace region at the opening of the drilled hole 1, also sand can be usedbut the hole must be securely closed directly at the opening by pressinge.g. a wooden plug into the hole.

It is also possible that the gas generator 3 is delivered to an end userwithout any liquid 5 filled in the second part 13. Then, the end userfills, before making the operations to set the gas generator in anactivated state such as installing an igniter 29, the second cavity 14with a liquid, e.g. water, in some suitable way.

The two parts 11, 13 of the gas generator can be rigidly attached toeach other as seen in FIGS. 1 and 2 or they can be separate parts whichin one embodiment are connectable to and detachable from each other asseen in FIGS. 3 and 4 and which in another embodiment are quite separateparts, see FIG. 5. As seen in FIGS. 3 and 4, the second part 13 can e.g.have a projecting portion 33 that can be detachably mounted to thebottom of the first part 11. The projecting portion can be introduced ina receiving recess that can be formed by the fact that the bottom plate21 of the first part is retracted from the lower edge of the outer walls17 of the first part, see FIG. 3. Alternatively, the second part 13 canhave an own top plug 31 including the projecting portion 33, see FIG. 4.The receiving recess can also be formed by the fact that instead of thebottom plate 21 a bottom closing structure 21′ is used that has a shapeof an inverted cup, see also FIG. 4. The projecting portion 33 can ifrequired or necessary be secured to the receiving recess in somesuitable way, e.g. using mating projections and recesses attaching thetwo parts to each other by a snapping action or by providing cooperatingthreadings, the securing means indicated schematically by the thicklines 35.

The thickness of the top plate-shaped portion 37 of the projectingportion that, when the two parts 11, 13 have been mounted to each other,comes in contact with the bottom plate 21 or the plate-shaped portion 39of the bottom closing structure 21′ can be designed not to be too firmor thick so that it can be easily broken by the pressure evolved whenthe combustible in the first part is ignited. For instance it can have athickness between 0.2 and 1.0 mm, in particular in the range of 0.2 to0.5 mm.

The gas generators 3 can also include two separate parts which then mayhave no special means for interconnecting them. Thus, as illustrated inFIG. 5, where the diameter of the drilled hole 1 is large exaggerated,one or more gas generators 3 can be inserted in the hole. Then first thesecond part 13 of a gas generator is inserted, this part having thestructure of a closed hose segment filled with e.g. water. The hosewalls 17′″ are made from a suitable material providing sufficientmechanical strength so that the second part can be handled withoutbreaking. Also, the material of the walls must of course be capable ofhermetically enclosing the fluid medium 5. Suitable materials include asabove solid hydrocarbons, e.g. polymers such polyethylene and rubber.The wall thickness can e.g. be in the range of 150 to 200 μm. Thediameter of the hose part is suitable adapted to the diameter of thedrilled hole 1, e.g. slightly smaller than the diameter of the hole forwhich it is designed. As above, the second part 13 can be collapsible sothat it can be stored, when it does not contain any liquid, in afolded-in or rolled-up state.

After the second part 13 of a first gas generator 3 has been inserted inthe drilled hole 1 so that it is relatively firmly engaged with thebottom of the hole, the first part 11 of the same gas generator isinserted so that it in turn is relatively firmly engaged with the outerend of the second part. This outer end and the bottom of the first partthus abut each other. In the case where the drilled hole is relativelylong or deep it may be suitable to use one or more additional gasgenerators. Then, the second part 13 of a second gas generator isinserted in the hole until the bottom end thereof abuts or is in arelatively firm contact with the top end of the first part of the firstgenerator. Thereupon, the first part 11 of the same second gas generatoris introduced. If suitable or required, one or more gas generators 3 canbe introduced in the hole in the same way. Finally, sand 7 is packed atthe mouth of the drilled hole 1. The sand plug or sand filling 7 can besealed by inserting a wooden plug 41.

The length of the sand filling 7 should be at least about 1.5 m in thecase where no wooden plug is used, as has been mentioned above. Thelength of each of the second parts 13 could suitably be larger than thelength of the sand filling.

For igniting the gas generator devices 3, e.g. electrical cables, notshown, can be used that extend from the igniters of the first parts 11of the gas generators to some external control unit, not shown.

It is also possible to exclude the innermost second, fluid filled part13, this case not being illustrated. Then, a first part 11 of a gasgenerator is introduced in the drilled hole 1, then a second part 13 ofa second gas generator, a first part of the second gas generator, etc.Thus, always a fluid filled second part 13 is located between two firstparts 11.

FIG. 7 is a schematic sectional view of an ignition unit 51 thatcorresponds to and can be used as the top plug 27 of FIGS. 1-4. Theignition unit comprises a body 53 that includes a lid 55, which can besubstantially flat and also forms the outermost end surface of the gasgenerator device 3 illustrated in FIGS. 1-4. From the inner surface ofthe lid 55 two ring-shaped shells project, an outer shell 57 and aninner shell 59. The two shells can e.g. be concentric with each other.The outer surface of the outer shell can be cylindrical, e.g.circular-cylindrical. The inner surface thereof can also be cylindricalit can as illustrated have some slope, e.g. it can have a frusto-conicalshape, so that the outer shell has a width at its inner free end that issomewhat smaller than the width in region where the outer shell 57connects to the lid 55, i.e. the outer shell can be tapering in thedirection of its free end. The inner shell 59 that generally can beconsidered a holding structure or holding device, delimits by its innersurface a space for receiving a cartridge or ignition fuse 61,corresponding to a detonator for activating an ordinary explosive. Thisspace can be cylindrical, e.g. circular cylindrical, with a relativelytight fit to the ignition fuse, that has its outer surface configuredcorrespondingly so that the ignition fuse 61 can be inserted in theinner space and safely held or secured therein. Alternatively oradditionally, the inner surface of the inner shell 59 can be configuredfor holding, by its shape, the ignition fuse, e.g. for providing asnapping action, such as by a suitably designed rim or bead, not shown,e.g. cooperating with an annular recess on the surface of the ignitionfuse. Also, the inner shell 59 can be tapering in the direction towardsof its free end, the outer surface of the inner shell then e.g. having afrusto-conical shape, so that the inner shell is thinner at its freeinner end than at the connection region to the lid 55.

The ignition unit 51 can be designed so that the outer shell 57 projectsa distance from the lid 55 that is longer than the distance at which theend or bottom surface of the ignition fuse 61 is located, taken from thelid 55. Thus, the inner end or end surface of the outer shell is locatedin a plane, perpendicular to the axis of the ignition unit, that has adistance 1 from a parallel plane through the free, inner end surface ofthe ignition fuse 61. When the ignition unit 51 is located at a charge63 that is to be ignited, such as at a plate 65 delimiting the charge, adistance 1 between the surface of the wall or top plate 65 and the innerend surface of the ignition fuse 61 is provided. Hence, there is a freespace at the inner, free end surface of the ignition fuse 61 and also afree space between the outer shell 57 and the ignition fuse and inparticular between the outer and inner shells 57, 59. These free spacesform buffering spaces protecting the ignition fuse 61.

The ignition fuse 61 in turn has an inner space or cavity 67 filled withan ignition compound 69. The ignition fuse can as illustrated haverelatively thick walls 71 surrounding the ignition compound and arelatively thin bottom 73 at the free, inner end of the ignition fuse.The cavity 67 can have a relatively elongated shape and thus has alongitudinal direction. E.g., the ratio of the length of the cavity tothe width or diameter thereof can be at least 1.5:1. The ratio of thelength to the width or diameter of the ignition fuse 61 is not criticalbut can e.g. be at least 1:1.

When the ignition unit 51 is activated and the ignition compound 69starts burning, a jet 75 of hot material is very rapidly produced, thehot material emitted from the inner, free end of the ignition fuse bybreaking the thin bottom of the ignition fuse 61. This allows the use ofsafe explosives or other burning material in the charge 63 to beignited, due to a high concentration of physical-chemical energy in theemitted jet. This may be particularly advantageous in mining andconstruction industries because the diameters of parts where the chargesto be ignited are located are not greater than 75 mm. That actually ajet of hot material is obtained is due the fact that the ignitioncompound 69 is located in such a chamber where the thickness of thewalls is considerably greater than the thickness of bottom. The gapbetween the outer shell 57 and the inner shell 59 protects the innershell and the ignition fuse 61 from mechanical influence when handlingand using the ignition unit 51.

In the embodiment of FIG. 7 the ignition unit can as illustrated bemounted to a gas generator where walls 77 of the gas generator projectinside the outer shell 57 with a tight fit for holding the ignitionunit. The ends of the gas generator walls can be in contact with theinner surface of the lid 55. The walls of the gas generator canalternatively be located at the outer side of the outer shell 57 asillustrated in FIG. 8 and in FIGS. 1-4. The inner end or end surface ofthe outer shell 57 then can be in contact with the wall or plate 65delimiting the charge. The plate 65 delimiting the charge 63 thencorresponds to the plate 23 of FIGS. 1-4.

The top surface of the ignition fuse 61, i.e. which is intended to be incontact with the lid 55, can as illustrated be beveled to allow an easyintroduction of the ignition fuse in the inner space of holdingstructure, i.e. the inner shell 59.

In an example, the bottom 73 of the ignition fuse 61 can have athickness in the range of 0.3 mm to 0.7 mm whereas the thickness of thewall can be at least 3 mm, e.g. in the range of 3 to 5 mm. The diameterand the height or length of the ignition fuse can be about 15 mm. Thedistance 1 can be at least 1 mm, e.g. in the range of 1 to 2 mm. Thematerial of the ignition fuse 61 should be selected so that it can standa long-lasting contact with the ignition compound 69, and can e.g.include a polymer such as polyethylene, polypropylene and polystyrene,in particular a high density polymer such as high density polyethylene(HD-PE).

An electric cable, not shown, as well as NONEL, non-electric shock tubelead line, or any other initiation system which provides the requiredcharacteristic, for activating, by resistive heating, the ignitioncompound 69 can pass through a hole 79 in the lid 53.

The cavities 67 of a multitude of ignition fuses 61 can simultaneouslybe loaded with the ignition compound 69 by placing empty fuses in holesin a table of a vibration device, not shown, and then providing anamount of the ignition compound to the surface of the table, using e.g.a rake and then making the table vibrate. This assures a uniform andequal filling of the cavities of the ignition fuses.

The material for burning or the charge in the first part 11, i.e. in thegas generator part, of the gas generator device 3 of FIGS. 1-4 caninclude a special composition as will now be described. This compositioncan as well be used in gas generators of other kinds and can generallybe used for splitting and/or destructing materials and objects.

Thus, a composition for splitting and/or destructing materials andobjects e.g. in a gentle mode is comprised in a gas generator 81, seeFIG. 9. The composition comprises, as described above, an oxidant thatis generally solid and is based on one or more chlorates and/orperchlorates of alkaline metals and/or earth metals, e.g. sodiumchlorate, and a solid material substantially being a hydrocarbon polymermaterial. The solid material is at least partly provided as a wallmaterial 83, 85 having a suitable shape enclosing or holding in cavitiesor spaces 87 the other components of the composition, such a shape e.g.including a plurality of tubes, a “honeycomb” structure having polygonalcells, corrugated strips or sheets or some similar shape. Furthermore,the solid wall material contains, in addition to the hydrocarbon polymermaterial, an energetic component such as aluminium or a metal havingsimilar burning characteristics, e.g. magnesium. The solid oxidant canbe provided in more or less granular shape and can in particular be apowder, e.g. having a particle size of 10 to 100 μm, in the same way asdisclosed in the cited Swedish patent 0201972-7 and is thus placed inthe spaces 87 formed by the solid wall material 83, 85. These spaceshave an adapted size. The thickness of the walls 83, 85 of the solidmaterial is selected considering the density of the oxidant. Thediameter of the spaces 57 can e.g. be selected to be 10 to 20 times thethickness of the walls. The inner diameter of the spaces for a solidwall material based on polyethylene can e.g. be in the range of 2.5 to 7mm in the case where the wall thickness is in the range of 0.05 to 0.7mm.

It appears that the addition of aluminium in the explosive compositioninstead as a powder, e.g. mixed with a granular oxidant such as sodiumchlorate, would of course, in the same way, increase the energy contentof the composition, as disclosed in the cited Swedish patent, but itwould also increase the possibility of the deflagration mode of thecomposition changing into a detonation mode associated with thedrawbacks resulting therefrom, see e.g. the discussion in the citedSwedish patent 0201972-7. Such drawbacks can include a reduced amount ofuseful stone blocks due to the increased amount of fissures and cracksin the blocks produced, an increased amount of small split stoneparticles and an increased distance that such stone particles fly in theexplosion, this resulting in a reduced work safety, and an increasedseismic load on the environment which is an inevitable result of thedetonation mode. Instead, aluminium or a similar material is introducedinto the solid material such as into the mass of the solid wallmaterial, e.g. into the solid hydrocarbon polymer or polymers, wherethis can done e.g. in the stage of producing the solid wall material.Aluminium can thus be incorporated in the wall material 83, 85 of thetubes, honeycomb cells, the corrugated strips or sheets or similarcontaining structures, such as in a granular form into the mass of thematerial forming the wall material or being applied thereto as one ormore layers inside and/or at the surfaces of the walls. The addedmaterial will still increase the speed of the burning and accordinglythe speed of pressure build-up as well as the energy content of thecomposition proportionally to the share thereof.

In a test, using a bomb of a constant volume, it was found that thelinear burning velocity, at ambient conditions, of a composition having1.5 wt % of aluminium incorporated in the wall material of a solidhydrocarbon material in the structures holding the other components ofthe composition increased by 3.5 to 5 times compared to a compositionaccording the cited Russian Federation patent No. 2152376 without theliquid component. The increase of energy content was about 10 to 15%.This resulted in a reduction of the full burning time of the compositionfrom 0.3 s to 0.1 s. It appeared from other experiments that thealuminium should be in incorporated with a concentration of at least 1.0wt % of the total mass of the composition.

Furthermore, the higher energy content results in the fact that the massof the composition that is needed to carry out a known work can bereduced. The choice of the definite composition, i.e. the percentage ofthe added burning velocity enhancing material such as aluminium in thecomposition, can be made taking into consideration data obtained whenmeasuring burning velocities at ambient conditions as well as in amanometric bomb, imitating natural conditions, in the same way asdisclosed in the cited Russian Federation patent No. 2152376.

It appears from experiments that in order to have some noticeable effectthe burning velocity enhancing material should be provided in aconcentration of at least 1.0 wt % of the total composition. Also,increasing the concentration of the burning velocity enhancing materialto more than 15 wt % of the total mass of the composition is noteffective, because, despite the increase of the temperature of thereaction products, the pressure evolved in the burning of thecomposition would then decrease since the amount of the condensed phaseresulting from the burning reaction increases and the amount of theresulting gaseous phase decreases accordingly.

It also appears from experiments that the concentration of the solidhydrocarbon polymer material including the burning velocity enhancingmaterial suitably is in the range of 4 to 21 wt % and even better in therange of 7 to 14 wt % of the total mass of the composition, in the casewhere sodium chlorate is used as the solid oxidant being substantiallythe rest of the total mass of the composition.

Since all components of the composition are generally available it canbe very easily prepared. The proposed compositions were all tested innatural conditions.

1. A gas generator device for breaking or splitting natural andartificial objects when inserted in a shaft and ignited to start aburning reaction in a deflagration or non-detonation mode in the device,the burning reaction accompanied by gases being produced and thereby acorresponding pressure, the gas generator device comprising an oxidantand a combustible compound or material, wherein the gas generator devicecomprises a first part having a first main cavity and a second parthaving a second main cavity, the oxidant and combustible compound arecontained in the first part and at least partly in the first maincavity, a liquid, in particular water, is contained in the second maincavity, and the first and second main cavities are separated from eachother by a bottom plate of the first part, the bottom plate forming thebottom of the first main cavity.
 2. A gas generator device according toclaim 1, wherein the first main cavity includes a plurality of parallelchannels, the parallel channels in particular being formed by aplurality of parallel tubes or having a cross-section of a substantiallyregular polygon shape, to form in particular a square or bar pattern ora honeycomb pattern, or formed by a corrugated foil introduced in thefirst main cavity.
 3. A gas generator device according to claim 1,wherein the outer walls of the first and second main cavities are formedby walls of one single tube extending over substantially the whole ofthe first and second parts.
 4. A gas generator device according to claim1, wherein the first and second part are detachably mounted to eachother.
 5. A gas generator device according to claim 4, wherein thebottom plate has the shape of an inverted cup, that is at least partlyinserted into the body of the first part, the inner space of the cupshape adapted to receive the top portion of the second part.
 6. A gasgenerator device according to claim 1, wherein the walls of the secondmain cavity are made from a material impermeable to the liquid containedtherein, the walls in particular being made at least partly fromimpregnated paper, a polymer material, rubber, or a metal such asaluminium.
 7. A gas generator device according to claim 1, wherein theoxidant comprises one or more chlorates and/or perchlorates of alkalinemetals and earth metals, in particular sodium chlorate NaClO₃.
 8. A gasgenerator device according to claim 1, wherein the combustible compoundor material comprises a hydrocarbon compound and/or a polymer such as ahydrocarbon polymer, in particular polyethylene, polypropylene and/orpolystyrene.
 9. A gas generator device according to claim 1, wherein thecombustible compound or material is at least partly contained in thefirst main cavity.
 10. A gas generator device according to claim 1,wherein the combustible compound or material is at least partly includedin the material of walls of the first main cavity.
 11. A method ofbreaking or splitting natural and artificial objects, comprising thesteps of: inserting at least one gas generator part in a shaft or bore,and igniting said at least one gas generator part to start a burningreaction in a deflagration or non-detonation mode in the device, theburning reaction accompanied by gases being produced and thereby acorresponding pressure, the gas generator part comprising an oxidant anda combustible compound or material, comprising the additional step of:inserting in the shaft or bore at least one container part containing anin compressible fluid or liquid, in particular water so that the shaftor bore is substantially filled with, except at a region at its mouth,said at least one gas generator part and said at least one containerpart.
 12. A method according to claim 1, wherein at least two gasgenerators parts are introduced and that between each pair of gasgenerators part a container part is placed.
 13. A method according toclaim 1, wherein in introducing said at least one gas generator part andsaid at least one container part, one container part and one gasgenerator part are introduced as one unit in the shaft or bore.
 14. Anignition unit for igniting charges of slowly burning substances,comprising an ignition fuse that includes a cavity containing anignition fuse and at its sides is surrounded by a free buffer spaceinside an outer protective shell, the buffer space protecting theignition fuse and the ignition compound therein when handling theignition unit, such as for mounting it to a charge.
 15. An ignition unitaccording to claim 14, comprising a body having substantially a cupshape or bowl shape including a lid from which the outer protectiveshell projects, the body further including an inner shell for holdingthe ignition fuse, the free buffer space formed between the outer shelland the inner shell.
 16. An ignition unit according to claim 15, whereinthe inner shell has an inner space receiving the ignition fuse, theinner space and the ignition fuse being adapted so that the ignitionfuse is securely held in the inner space.
 17. An ignition unit accordingto claim 15, wherein the inner shell has an inner space receiving theignition fuse, the inner space and the ignition fuse being adapted sothat the ignition fuse can be easily introduced in the inner space. 18.An ignition unit according to claim 14, wherein the ignition fuse, atits end facing a charge to be ignited, has a bottom surface that isretracted from a plane passing through the free end of the outerprotective shell, i.e. is located at a distance of said plane takeninwards, towards the center of the ignition unit.
 19. An ignition unitaccording to claim 14, wherein the ignition fuse has a bottom whichdelimits the cavity and which, when the ignition unit is adapted forigniting a charge, is directed to or facing a surface of the charge, andfurther having sidewalls connected to the bottom and extending away thesurface of the charge, the sidewalls having a thickness that isconsiderably larger than the thickness of the bottom, so that when theignition unit is active and the ignition compound is made to burn, a jetof hot material is produced and emitted from the cavity containing theignition compound, the jet breaking the bottom of the cavity and beingdirected to the surface of the charge
 20. An ignition unit according toclaim 19, wherein the thickness of the bottom is in the range of 0.3 mmto 0.7 mm.
 21. An ignition unit according to claim 14, wherein thematerial of the ignition fuse, in particular of the walls and bottom ofthe cavity therein, include a polymer material, in particular one ormore substances selected among polyethylene, polypropylene andpolystyrene, such as a high-density polymer.
 22. A gas generator forsplitting rock and block stones and for destructing natural andartificial objects in a gentle mode, the gas generator comprising asolid oxidant, in particular sodium chlorate, provided in a granularform and a solid wall material substantially of a solid hydrocarbonpolymer material provided in a suitable shape, in particular in theshape of tubes, a honeycomb structure, corrugated strips or sheets or aplurality of containers, the solid wall material holding or enclosingthe solid oxidant, wherein a burning velocity enhancing material, inparticular aluminium, magnesium or a similar metal, is incorporated inthe solid wall material.
 23. A gas generator according to claim 22,wherein the burning velocity enhancing material is incorporated in agranular form in the mass of the solid wall material.
 24. A gasgenerator according to claim 22, wherein the burning velocity enhancingmaterial is applied as a layer or layers in the walls or at the surfaceof walls of the solid wall material.
 25. A gas generator according toclaim 22, wherein the burning velocity enhancing material is provided ina concentration of at least 1% of the total mass of the composition. 26.A gas generator according to claim 22, wherein the burning velocityenhancing material is provided in a concentration of 1.0-15 wt % of thetotal mass of the composition.
 27. A gas generator according to claim22, wherein the concentration of the solid hydrocarbon polymer materialincluding the burning velocity enhancing material is 4-21 wt %, inparticular 7-14 wt %, of the total mass of the composition and that therest of the total mass of the composition is substantially sodiumchlorate.
 28. A gas generator according to claim 22, wherein the solidhydrocarbon polymer material includes one or more selected amongpolyethylene, polypropylene and polystyrene and similar polymers.
 29. Agas generator according to claim 22, wherein the solid oxidant includesone or more chlorates and/or perchlorates of alkaline metals and/orearth metals, in particular one or more substances selected among sodiumchlorate, potassium chlorate, sodium perchlorate and potassiumperchlorate.